\clearpage
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%\addcontentsline{toc}{section}{Bibliografia}
\renewcommand*{\refname}{} % This will define heading of bibliography to be empty, so you can...
\section{Bibliografía}     % ...place a normal section heading before the bibliography entries.
\begin{thebibliography}{}
\bibitem{Mogul}
    Mogul, J., Postel, J., \\
    \emph{``Internet Standard Subnetting Procedure''} \\
    RFC 950, 1985.
    
\bibitem{DNS for Rocket Scientists}
  \emph{``DNS for Rocket Scientists''} \\
  Disponible en: http://zytrax.com/books/dns/.

\end{thebibliography}